In a delayed transfusion reaction, when is the causative antibody typically detectable after transfusion?

In a delayed transfusion reaction, the causative antibody typically becomes detectable between 3 to 7 days after the transfusion. This time frame aligns with the immune response dynamics that occur after the initial exposure to the transfused red blood cells.

During a delayed transfusion reaction, the body’s immune system recognizes the transfused red blood cells as foreign due to the presence of antigens that the recipient may not have been previously exposed to. In response, the immune system takes time to produce specific antibodies against those antigens. The heightened antibody production usually begins around the 3 to 7 days mark, which explains why this window is significant for detection purposes.

In contrast, the shorter time frames mentioned in the other options do not accurately reflect the immunological response time needed to develop detectable antibody levels after a transfusion. Additionally, the longer time periods provided in the latter options go beyond the typical range for a delayed transfusion reaction, as antibodies involved in such reactions would usually be detectable well before reaching 60-120 days.